> All I need in a browser is the ability to browse (tabbed) while blocking ads.

You can do this in Firefox, with several great ad-blocking extensions, such as uBlock Origin or Adnsaueum.

> Browsers anymore have become walled gardens what with their add-on web stores, garbage like Pocket, sync, etc. I don't want any of that. Browsers could all be more like the old-school Konqueror, in the sense that one could import ad block lists at will without resorting to visiting store.

Firefox allows you to remove what you don't need, especially Pocket. Sync is optional.

> No telemetry. No built in search for a certain search engine.

There are specific Firefox configurations that disable telemetry: https://github.com/CrisBRM/user.js/blob/master/user.js